The invention relates to a heat exchanger, for example one used in the automotive field and more specifically to a heat exchanger comprising a plurality of tubes for the circulation of a heat-transfer fluid, the ends of said tubes opening into manifolds, and reservoirs of thermal storage material in contact with the tubes so that the storage material and the heat-transfer fluid exchange heat with one another.
The purpose of a heat exchanger is to provide an exchange of heat between a fluid circulating within a plurality of tubes, known as a heat-transfer fluid, and an external, fluid passing through the heat exchanger. In the case of a motor vehicle air-conditioning system, the external fluid may be air intended to be blown into the cabin of the vehicle. The exchange of heat is used to cool the blown air.
The tubes conventionally open into manifolds, one function of which is to place all or some of this plurality of tubes in fluidic communication.
The heat exchanger is connected to the remainder of the fluid circulation circuit, for example a motor vehicle air-conditioning circuit. The fluid is circulated through the circuit by a compressor driven directly off the engine of the motor vehicle.
In consequence, when the vehicle engine is not running, there is no circulation of fluid through the circuit and exchange of heat between the air and the heat-transfer fluid cannot take place. The air blown into the cabin of the vehicle is therefore no longer cooled. This situation is becoming all the more problematical since recent fuel-economizing systems anticipate automatically switching the engine off when the vehicle comes to a standstill, often depriving the cabin of cooled air.
It is known practice to provide a heat exchanger with reservoirs of thermal storage material associated with the tubes through which the heat-transfer fluid circulates.
For example, French patent application FR 2 847 973 provides a heat exchanger equipped with special tubes that have a plurality of passages for circulating heat-transfer fluid and a plurality of longitudinal cavities adjoining said passages. These longitudinal cavities accommodate a thermal storage material, while the passages allow the refrigerant to circulate. Through contact between the cavities and the passages, the storage material and the heat-transfer fluid can exchange heat with one another.
Thus, when the vehicle engine is running, the refrigerant cools both the air passing through the heat exchanger and the thermal storage material. The thermal storage material then releases the coldness (more specifically the cold energy) to the air passing through the heat exchanger when the engine is switched off.
Although these special tubes have proved satisfactory, they are relatively complicated and expensive to produce.